Radioactive decay - waves and particles Study Guide

The electricity supplied to homes in the United Kingdom is a specific type of electrical current known as alternating current (a.c.). Unlike direct current (d.c.), which flows in only one direction, alternating current regularly reverses its direction of flow. This constant change is why it's called 'alternating'. The rate at which the current alternates direction is described by its frequency. In the UK, the domestic supply has a frequency of 50 Hz (Hertz), meaning the current changes direction and completes a full cycle of alternation 50 times every single second. This rapid change is crucial for the efficient operation of many common household appliances.

Alongside frequency, another important characteristic of the domestic supply is its voltage. Voltage is a measure of the electrical potential difference, which provides the 'push' needed to make the current flow. For the domestic supply in the UK, this voltage is approximately 230 volts (V). This specific voltage level is standardised across the country to ensure that appliances designed for the UK market can operate safely and effectively. Devices such as televisions, washing machines, and kettles are all designed to run on this 230 V, 50 Hz a.c. supply. Understanding these characteristics is fundamental to appreciating how electricity powers our homes and why electrical safety is paramount.

Understanding typical speeds helps us estimate and comprehend motion around us. Speed is a scalar quantity that measures how fast an object is moving, defined as the distance covered per unit of time. While exact speeds can vary greatly, it's useful to have a general idea of common speeds for different activities and phenomena. For instance, humans walking typically cover distances at around 1.5 meters per second (m/s). A brisk run might increase this to about 3 m/s, and cycling can achieve speeds of 6 m/s or more on flat ground. Transportation systems like cars on urban roads move significantly faster, often around 13 m/s (approx. 30 mph), while trains can reach much higher speeds, sometimes exceeding 50 m/s. Wind speeds are highly variable, from a gentle breeze at a few meters per second to gale-force winds exceeding 30 m/s. Sound, on the other hand, has a fixed speed in a given medium; in air at standard conditions, sound travels at approximately 330-340 m/s, which is significantly faster than any typical human or vehicle speed. These benchmark values provide a framework for evaluating the scale of motion in various situations.